Ours were a little pushy before we were free ranging them, now I open the coop door, about 90% of the birds run out and head around to peck at the dirt, the cracked corn I drop on the ground, or to eat the little maple trees that grow everywhere. I will usually fill the feeder and put it outside and some of them will go over and eat, but not all of them. Then I fill the water and usually some rotate out from the feeder to get water...I have 12 Cornish roasters, and 26 Cornish X and I am only using one 12 pound galvanized feeder right now, and for the most part, they all eat out of it pretty easily. I am enjoying their personalities as we've allowed them to grow one more and I've spent more time with them. They are trying to fly and they fly about as effectively as any basketball shaped item would. They get about 2 feet off the ground, but they love running down the little hill in the back yard and "catching air"...pretty funny. They had almost zero personality when all I did was take the time to toss their food in, but now that they get out and run and play (they even peck at tennis balls) they are much calmer and more curious and friendly. I sort of think when you make their life only about food, then that is all they will care about, and all that matters, so maybe that is why some get aggressive about it?
In fact the morning after I filled the feeder, my 2 year old sat at one of the feeder "spots" around the round feeder so he could be close to some of the birds and he would pat them and tell them "nice" and ever checked out their feet and little nails and they were all fine with him, he didn't get pecked even once.